Knowledge of skin cancer risk factors and the subsequent success of prevention interventions clearly depends upon the accuracy of the assessment of UV-risk behaviors, such as intentional radiation exposure and protection. The vast majority of studies in the skin cancer literature rely on un-validated, single-item global retrospective measurements of their UV-risk outcome factors. There is an extensive literature documenting the potentially serious errors and systematic biases to which retrospective measures are subject to. There is preliminary data that indicates that electronic online diary assessments of UV-risk behaviors avoid many of the biases and errors associated with retrospective measures. However, electronic diary assessments are more expensive and less acceptable to respondents than global measures, making them problematic for many research projects. This proposal aims to examine the reliability and validity of commonly used single-item retrospective assessments of UV exposure behavior using electronic diary measures as criterion variables. It also proposes to compare the accuracy of a composite retrospective index to the single-item measures, and evaluate the relationship of objective skin color measures to daily UV exposure reports. Two-hundred participants will be recruited for this study. Objective skin color measures will be taken during the wintertime, and then at the beginning and end of one summer. Participants will also record their UV-risk behaviors during this same summer using daily electronic online diaries. At the end of summer, participants will complete a questionnaire which assesses UV-risk behaviors using a variety of global retrospective measures. Diary data will be used to validate the global measures, and compare their relative accuracy. Diary data will also be used to explore the dynamics of skin color change. If successful, this proposal will significantly improve the assessment of UV-risk behavior in the skin cancer prevention literature. Public Health Relevance: This research will improve the ability to accurately measure behaviors that lead to skin cancer development. This improvement in the measurement of skin cancer related behaviors should improve prevention efforts and lead to the prevention of future skin cancer. [unreadable] [unreadable] [unreadable]